Data processing in intra-site handover

ABSTRACT

The technology involves data processing during intra-site handover procedures. At least two directional antennas of a base station receive user data carrying signals originating from a mobile units positioned in an intra-site handover area defined by the overlapping radio coverage of the antennas. The directional antennas performs an initial data signal detection of the received data signals resulting in detected user data, which typically results in a loss of radio performance of the antenna. The detected user data from the directional antennas is then jointly processed to generate processed user data. The performance loss is compensated by providing differential antenna gain of the directional antennas within the handover area. As a result, a similar radio coverage in this area as prior art solutions is obtained but with a less complex antenna-related design.

This application is the US national phase of international applicationPCT/SE2004/001067, filed 30 Jun. 2004, which designated the U.S., theentire content of which is hereby incorporated by reference.

TECHNICAL FIELD

The technology generally relates to data processing in communicationssystems, and in particular to data processing during intra-site handoverprocedures in such systems.

BACKGROUND

A typical cellular radio communications system comprises a number of(radio) base stations (RBSs) providing communications resources tomobile units and user equipment present in the system. A base stationoften has multiple (e.g. at least two) associated directional antennaunits that are able to provide the communications services throughseveral separated sectors or cells within the total coverage area of thebase station.

In order to enable seamless movement of a mobile unit between differentcells during a communications session, the radio coverage areas ofneighboring cells typically, at least partly, overlap. Such anoverlapping coverage area is denoted handover area or region in the art.

The size of the handover area depends on measurement control parameters.A minimum region requirement is that a mobile unit travelling from onebase station and/or cell to another has time to measure, report,configure and synchronize to the new base station and/or cell before thecommunications link to the old cell has to be dropped due toinsufficient signal quality.

There is a clear distinction in operation between moving from cells ondifferent base stations (or sites) and cells on the same site, theformer being denoted soft handover and the latter is a so-called softerhandover.

For softer (intra-site) handover, the single base station simultaneouslytransmit, using its different directional antennas, the same informationover each of the cells to the mobile unit, thus, creating transmit macrodiversity gain. Correspondingly, signals communicated from the mobileunit are received through the different cell radio hardware (antennaequipment) in the single base station. The received unprocessed signalsfrom these cells are then usually directly combined using amaximal-ratio combining (MRC) or equivalent configured receiver ordetector. MRC is generally superior compared to the informationcombining techniques used for soft handover, where themobile-unit-originating data are received and detected by different basestations.

However, softer handover and MRC signal reception implies restrictionsand complexity to the antenna-related equipment in the base stations.For example, in softer handover all internal cells radio chains of agiven base station have to be fully accessible for all receivers in thebase station. This complexity, thus, will be affected by the number ofdiversity paths or radio chains available, which can be quite high,especially for multi-antenna based RBS configuration or arrangement. Inaddition, the increased number of communication paths for the signal,due to the softer handover with corresponding control signaling in theradio access network, results in more signals transmitted by the basestation that, by constructive combining of the transmitted energy, inturn leads to an increased coverage and/or transmission area. Thisincreased coverage and/or transmission area will effect the interferencesituation in the system by increasing the interference levels. Theincreased number of communications paths also takes capacity resourcesfrom the system. In summary, seamless mobile communications utilizingsofter handover and MRC generally yield the best statistical reductionof fading, however, this comes as a cost of more complex antennaequipment, increased interference and reduced capacity.

SUMMARY

The technology described in this application overcomes these and otherdrawbacks.

It is a general object to provide an enhanced intra-site handoverprocedures in communications systems.

It is another object to provide a data processing applicable duringintra-site handover procedures in communications systems.

Yet another object is to provide a simple antenna-related base stationarchitecture applicable for intra-site handover procedures incommunications systems.

Briefly, the technology described in this application involvesintra-site handover procedures and data processing during such handoverprocedures in radio communications systems. A mobile unit positionedwithin an intra-site handover area and connected to at least twodirectional antenna units of a base stations generates and transmitssignals carrying user data. These user data signals are received by thedirectional antenna units and are initially detected and processedresulting in first and second detected (demodulated) user data. Due tolimitations and non-optimal performance of the antenna-related units,this data signal detection contributes to a performance loss, whichgenerally results in that the directional antenna units would not beable to provide as a large radio coverage in the handover area and stillbeing able to successfully process and interpret the user data signals.

In order to balance or compensate for the detection performance loss ofthe initial data signal detection and processing, the antenna beam of atleast one of the directional antenna units involved in the intra-sitehandover procedure is adjusted in order to increase the antenna gainwithin the intra-site handover area. Thus, instead of providing acomplex antenna and base station arrangement to enable increasedperformance and radio coverage in the handover area, the inventors solvethis by increasing the antenna gain in this handover area. This meansthat higher antenna gain levels are obtained in this portion of theantenna beam or cell, at least during the intra-site handover procedure,compared to the prior art antenna arrangements.

In addition, the detected user data from the directional antenna unitsare then jointly processed to give the demodulated and processed userdata. This jointly data processing can be realized as a data setselection and/or combining. The final processed user data can then beforwarded to other network units in the communications system and/ortransmitted to other mobile units.

This jointly processing may advantageously also use soft information,e.g. quality indicators or estimations, associated with the respectivedetected user data in order to enhance the performance of thedirectional antenna further.

The differential adjustment of antenna gain can be realized by aredistribution of the directivity of the directional antenna unit(s)into this handover area, which is discussed in more detail below.Generally, the purpose of this antenna gain adjustment is to balance theradio performance loss during the data signal detection and processingso that the resulting total performance in connection of the user dataprocessing still is adequate and enables adequate radio coverage in thehandover area.

This differential increase in antenna gain and coverage can beimplemented by redistributing the directivity in the horizontaldimensional from other parts of the antenna diagram. For example, the (3dB) beam width of the antenna beam can be increased, possibly at thesacrifice of maximum obtainable gain in the remaining portion of theantenna beam. However, the resulting minor reduction of peak antennagain coming from the redistribution of directivity in the horizontaldimension can be compensated by a slight increase of the antenna heightand/or reduced losses in the communications system.

Alternatively, or in addition, the adjustment of antenna gain in thehandover area can be obtained by (virtually) dividing the antenna beamof the directional antenna into different beam sectors and then applyinga differential adjustment of the shape of this individual beam sectorsbased on different objectives. The division preferably results in atleast a handover beam sector and a main beam sector. The shape of thehandover beam sector is then adjusted to provide at least a minimumantenna gain (radio coverage) and preferably a minimum angular intervalwithin this beam sector.

The increase in antenna gain can be obtained by mechanically adjustingthe mechanical structures, e.g. baffles, ground plane and/or secondaryradiators, of the directional antenna unit(s). Furthermore, if thedirectional antenna unit is a group antenna with multiple antennas, thedesired beam shape can be obtained by adjusting the relative amplitudeand/or phase excitations of the antennas.

The jointly processing step can be implemented as a selection process,where signal or link qualities for the communications channels betweenthe mobile unit and the directional antenna units are estimated andcompared. Thereafter, the processed user data is generated based on thedetected user data associated with the communication channel having thecurrent best link quality. Alternatively, the detected user data fromthe directional antenna units in the base station can be combined inorder to increase or improve the correctness of the information content.In either case, the jointly processing can be performed in the relevantbase station or in an external network unit, e.g. a radio networkcontroller or base station controller.

The technology described in this offers the following advantages:

-   -   Provides a less complex and costly antenna-related and base        station design compared to prior art designs involved in        intra-site handover;    -   Decreases interference levels due to a reduction in the number        of necessary communications paths for user data signals;    -   Releases communications resources and increases capacity due to        a reduction in the number of necessary communications paths for        user data signals; and    -   Provides radio coverage that remain similar to or improve        compared with the complex and costly prior art antenna-related        solutions.

Other advantages will be appreciated upon reading of the belowdescription.

SHORT DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic overview of a portion of a communications system;

FIG. 2 is a schematic diagram illustrating two neighboring antenna beamscomparing the gain in the handover region between soft and softerhandover;

FIG. 3 is a flow diagram illustrating the data processing method;

FIG. 4 is a schematic diagram illustrating an example of two neighboringantenna beams optimized;

FIG. 5 is a flow diagram illustrating an embodiment of the antenna gainincreasing step of the method of FIG. 3;

FIG. 6 is a flow diagram illustrating another embodiment of the antennagain increasing step of the method of FIG. 3;

FIG. 7 is a schematic diagram illustrating another example of twoneighboring antenna, beams optimized;

FIG. 8 is a schematic diagram illustrating a further example of twoneighboring antenna beams optimized;

FIG. 9 is a flow diagram illustrating an embodiment of the jointlyprocessing step of FIG. 3;

FIG. 10 is a flow diagram illustrating another embodiment of the jointlyprocessing step of FIG. 3;

FIG. 11 is a flow diagram illustrating an embodiment of the datareception step of FIG. 3;

FIG. 12 is a schematic block diagram illustrating a base station;

FIG. 13 is a schematic block diagram illustrating an embodiment of theantenna beam adjuster of FIG. 12;

FIG. 14 is a schematic block diagram illustrating another embodiment ofthe antenna beam adjuster of FIG. 12;

FIG. 15 is a schematic block diagram illustrating an embodiment of thedata processor of FIG. 12;

FIG. 16 is a schematic block diagram illustrating another embodiment ofthe data processor of FIG. 12; and

FIG. 17 is a schematic block diagram illustrating a radio networkcontroller.

DETAILED DESCRIPTION

Throughout the drawings, the same reference characters will be used forcorresponding or similar elements.

The technology described in this application relates to data processingin connection with intra-site handover procedures in radiocommunications systems and provides a novel intra-site handoveroperation that results in reduced antenna complexity and reducedinterference levels in the communications systems but with radiocoverage and capacity that will remain or improve in comparison to priorart systems.

FIG. 1 is a schematic overview of a portion of a radio communicationssystem 1, to which the teachings of this application can be applied. InFIG. 1 only arrangements and units directly involved in the inventionare shown in order to simplify the illustration. The technologydescribed in this application can typically be applied to differenttypes of communications systems 1 including a GSM (Global System forMobile communications) system, different CDMA systems, e.g. a WCDMA(Wideband CDMA) system, a Time Division Multiple Access (TDMA) system, aFrequency Division Multiple Access (FMDA) system or any other radiocommunications systems utilizing whatsoever multiple access method, e.g.an Orthogonal Frequency Division Multiple Access (OFDMA) system.

The radio communications system 1 comprises a number of radio basestations (RBSs) or base station transceivers 100, 200, of which only twoare illustrated in the figure. The RBSs 100, 200 enable utilization ofcommunications services within their provided radio coverage areas 10,20.

In the figure, the RBS 100 has been illustrated with multiple associateddirectional antenna units 120, 140, 160 that provides radio coverage indifferent sectors or cells 12, 14, 16 of the total radio coverage area10 of the site where the base station 100 is located. The RBS 100 caninclude three directional antenna units 120, 140, 160 with differentmain directions as is illustrated in the figure. However, the technologydescribed in this application can also be applied for another basestation configuration that includes multiple, i.e. at least two,directional antennas, e.g. 2, 3, 6 or 12 directional antennas.

The directional antennas 120, 140, 160 could be configured for togetherproviding total radio coverage 10 within a general area surrounding theRBS 100, e.g. circular, hexagonal or star-shaped. However, it is alsopossible that the total coverage area 10 of the directional antennas120, 140, 160 arranged in a RBS 100 only constitutes a portion or sectorof a general area. For example, if the directional antenna 120 isomitted, no radio coverage will be provided by the RBS 100 within thearea denoted 12. This may be the case when the network operator is notinterested in providing radio coverage and, thus, communicationsservices within certain areas that may e.g. include large mountains orother objects, rendering the area inaccessible for the users of mobileunits 400. In either way, neighboring cells 14, 16 associated with theRBS 100 or site preferably partly overlaps 15 in order to enable aseamless movement of a mobile unit 400 with an ongoing communicationssession. Similarly, cells 12, 22 of neighboring sites or base stations100, 200 also partly overlaps 13.

In order to enhance understanding, a short discussion of intra-site orsofter and inter-site or soft handover procedures as exemplified by aWCDMA radio communications system 1 follows. As is known in the art, themobile unit 400 intermittently or periodically performs signal qualitymeasurements of communications channel(s) in the so-called active set.This active set includes those cells 14, 16 to which the mobile unit 400currently is connected. The mobile unit 400 preferably also measuressignal quality of communications channels in the so-called candidateset.

This candidate set includes neighboring cells 12 to the cell(s) 14, 16in the active set. These signal quality measurements are then reportedto a central unit connected to and managing the base stations 100,represented by a radio network controller (RNC) 300 in the figure. TheRNC 300 then verifies, based on the received measurement data, whether ahandover procedure should be triggered and executed for the mobile unit400.

Starting with soft handover, the mobile 400 is then present in ainter-site handover area 13, in which the radio coverage of at least twocells 12, 22 of different sites or RBSs 100, 200 overlaps. Thedirectional antennas of these cells 120, 220 have been commanded by theRNC 300 to detected the same user data signal originating from themobile unit 400. In addition, signal or link quality measurements areperformed on the communications link between the mobile unit 400 and thetwo antennas 120, 220. The detected and processed user data is thenforwarded together with the link quality data from the two base stations100, 200 to the RNC 300. The RNC 300 will then typically perform aselection diversity combining (SDC) on the two received data streams byselecting, per data frame or block basis, the processed user data fromthe communications link that currently has the best link quality asdetermined based on the quality measures. Thus, generally the user datasignal content as received by only a single directional antenna ismainly used for further processing in the communications system 1.

However, during intra-site handover the mobile unit 400 is positioned inan intra-site handover area 15, where the radio coverage of twoneighboring cells 14, 16 of a same site partly overlaps. In this form ofhandover, the radio chains from all receivers (directional antennas 120,140, 160) of the relevant base station 100 have to be interconnected. Inthe illustrated example of FIG. 1, this will result in 6 radio chains,in case each directional antenna 120, 140, 160 is equipped with tworeceivers (creating uplink diversity reception). The receivedunprocessed user data carrying signals from all available receivers andradio chains are directly combined, typically according to maximum ratiocombining (MRC) or an equivalent combining technique, in the basestation 100. Thus, by using unprocessed data signals from multiplereceivers in the data combination a superior data processing andimproved detection performance is obtained compared to the selectioncombining of soft handover. However, this comes as a cost in increasedantenna-related equipment and base station architecture. In addition,the interference levels in the system will increase as was discussed inthe background section. Furthermore, the increased number ofcommunications paths takes communications resources, e.g. codes,frequencies and/or time slots, from the system 1, thereby affecting thecapacity in the system 1.

FIG. 2 is an antenna diagram illustrating the maximum radio coverage(antenna beam) 40, 60 of two neighboring cells according prior artsolutions. Firstly, assume that the two cells are of different sites,i.e. they are arranged in physically separated base stations. Byemploying the prior art data processing during soft handover, theperformance and, thus, the resulting maximum radio coverage in thehandover area is according to the line denoted soft HO in the figure.However, by applying the more complex MRC-based data processing duringsofter handover, a higher performance and radio coverage (softer HO inthe figure), within this handover area is typically obtained. Thus,softer handover generally results in higher performance compared to softhandover within the handover area when employing prior art techniques.

The technology described in this application provides similarperformance and radio coverage as the prior art data processing insofter handover but with less complex and expensive hardware equipment,reduced interference levels and increased system capacity.

FIG. 3 is flow diagram of a method of processing user data according toan example embodiment. In this method, user data carrying signalsoriginating from a mobile unit positioned in an intra-site handoverarea, where the radio coverage of two neighboring directional antennaunits of same base station or site overlaps, are processed during thehandover procedure. Instead of providing a complex antenna-related andbase station arrangement to enable increased performance and radiocoverage in the handover area, the antenna gain of a directional antennain the handover area is increased in step S1. This means that higherantenna gain levels are obtained in this portion of the antenna beam orcell, at least during the intra-site handover procedure, compared to theprior art antenna arrangements. As was discussed above, during anintra-site handover, the mobile unit is simultaneously connected to atleast two neighboring directional antenna units arranged in the sameRBS. In this antenna gain increasing step S1, the antenna gain in thehandover area of one of these at least two directional antenna units canbe adjusted and increased. Alternatively, the antenna gain of both theneighboring antenna units is increased. This differential adjustment ofantenna gain can be realized by a redistribution of the directivity oravailable antenna energy/gain of the directional antenna unit(s) intothis handover area, which is discussed in more detail below. Generally,the purpose of this antenna gain adjustment is to compensate or balancefor the performance loss, including radio coverage loss, during the datasignal processing using the somewhat more simple signal demodulation anddetection.

In a next step S2, the two neighboring directional antenna units receive(undistorted) user data RF signals originating from the mobile unitpositioned in the handover area. The user data signals received by thedifferent antenna units include the same information content. However,due to detrimental effects of e.g. channel fading and co-channelinterference the quality of the data signals received by the at leasttwo antenna units may differ. The RNC or RBS has, thus, ordered the twodirectional antenna units to connect (listen) to this mobile station sothat the communicated signals from the mobile station is receivedthrough both the cells radio hardware equipment (directional antennaunits) in the single RBS. An initial signal processing or detection isthen performed in the respective directional antenna unit or inconnection thereof in step S3. This user data signal detection includesthose initial steps that are generally performed in a receiver,including e.g. demodulation, A/D-conversion, user data regeneration anddecoding. However, due to limitations and finite operation of thedetection equipment this signal detection will be somewhat reduce themaximum performance of the directional antenna, e.g. as manifested inprovided radio coverage area. Thus, due to this performance(information) loss, the directional antenna units would not be able toprovide as a large radio coverage in the handover area and still beingable to successfully process and interpret the user data signals as thecomplex prior art MRC solutions if not the antenna gain in this handoverarea had been increased in step S1. The increased antenna gain couldthen be viewed as a compensation for the usage of a less complex andexpensive user data processing technique and for the lack of performancegain that would result from MRC and equivalent combining of unprocessedRF signals. In the final step S4, the first and second detected anddemodulated (reduced-information) data from the two neighboringdirectional antenna units is then jointly processed. As a result of thisjointly processing, processed user data that can be employed by thecommunications system, e.g. transmitted to a second mobile unit oranother network unit, is obtained. This jointly processing can berealized as a selection between the detected user data with the bestdata content, e.g. as determined based on signal quality comparisons.Alternatively, a user data combining can be employed in this jointlyprocessing of step S4. The method then ends.

In a first example embodiment, the detected (demodulated) user dataincludes a control data portion and a payload data portion. The jointlyprocessing of step S4 can then be performed either on the control dataportion, payload data portion or the control and payload data portion ofthe detected user data.

Furthermore, the jointly processing can be performed in the RBS, inwhich the directional antenna units are arranged, for example after theinitial signal detection (demodulation) or after decoding. The resultingprocessed user data will then be transmitted from this RBS to externalunits, e.g. a RNC. Alternatively, the generated (first and second)detected user data is transmitted from the RBS to an external jointlydata processor, e.g. as provided in the RNC or BSC (base stationcontroller) connected to the RBS.

FIG. 4 is an antenna diagram comparing the radio coverage of twoneighboring directional antenna beams of a prior art solution withoutMRC combining (dashed lines) 40, 60 with the corresponding coverage 45,65. As is evident from the figure, the antenna beams 45, 65 of the twodirectional antenna units partly overlaps in the handover area orregion. The antenna gain of at least one of these neighboringdirectional antenna units is then increased in this handover area. As aresult, an increased performance and coverage in this portion of thetotal radio coverage area is obtained.

This differential increase in antenna gain and coverage can beimplemented by redistributing the directivity in the horizontaldimensional from other parts of the antenna diagram. For example, the (3dB) beam width of the antenna beams 40, 60 can be increased, possibly atthe sacrifice of maximum obtainable gain in the remaining portion of theantenna beam 40, 60. However, the resulting minor reduction of peakantenna gain coming from the redistribution of directivity in thehorizontal dimension can be compensated by a slight increase of theantenna height and/or reduced losses in the communications system.

The increase in antenna gain can, e.g. due to redistribution of antennadirectivity, be obtained by mechanically adjusting, e.g. moving and/orrotating, a mechanical structure of the directional antenna unit(s).Such a mechanical structure can be the baffles around the antennaradiators, the ground plane behind the antenna radiators and/or astructure that couples energy from the radiators, e.g. secondaryradiators. Furthermore, if, the directional antenna unit is a groupantenna with multiple antennas, the desired beam shape can be obtainedby adjusting the relative amplitude and/or phase states or excitationsof the antennas. As the person skilled in the art understands, anyprocedure that results in an increase in antenna gain and coveragewithin this handover area could be used.

As a result, similar radio performance as for the complex MRC-based userdata processing in intra-site handover can be obtained but with muchless complex and costly equipment.

FIG. 5 is a flow diagram of an embodiment of the antenna gain increasingstep of FIG. 3. In the step S1, the (3 dB) beam width of the antennabeam of a directional antenna unit is increased, e.g. by redistributingthe directivity of the antenna unit into the handover area. The methodthen continues to step S2 of FIG. 3.

FIG. 6 is a flow diagram of another example embodiment of the antennagain increasing step of FIG. 3. In this embodiment different beam sectorportions of the antenna beam of a directional antenna unit are defined.The shape of these beam sectors is then optimized based on differentobjects and requirement. In a preferred embodiment, at least a first orhandover related beam sector of the total antenna beam of a directionalantenna unit is defined. This beam sector definition preferably isperformed by (virtually) dividing the antenna beam of the directionalantenna unit into at least the handover beam sector and a second or mainbeam sector in step S21. In step S22, the shape of the handover beamsector is adjusted by providing a minimum antenna gain of thedirectional antenna in this handover beam sector. Thus, the antenna gainin the beam sector should exceed a minimum threshold, the value of whichis determined based on the handover parameter settings in the system. Inaddition, or alternatively, the angular interval of this handover beamsector is preferably provided larger than an angular threshold. Thevalue of this angular threshold is determined based on the handoverparameter settings in the system. Thus, the angular size of thishandover beam sector will be adapted to (intra-site) handoverrequirements and the threshold value is chosen to allow triggering andcompletion of a handover procedure for a mobile unit crossing thehandover beam sector. In the optional step S23 the shape of the mainbeam sector is optimized or adjustment. This optimization is performedby maximizing the antenna gain of the directional antenna in this mainbeam sector. The method then continues to step S2 of FIG. 3.

The handover beam sector is preferably defined as that portion of theantenna beam where the difference in received signal level associatedwith the directional antenna unit and with its neighboring antenna unitin the handover beam sector is smaller than a first threshold T₁. Therelevant signal level is in a first embodiment, the signal strengthlevel as measured by the directional antenna(s). This signal level ismeasured and determined based on data transmitted by a mobile unit andreceived by the antenna. In a second embodiment, the received signallevel is determined by the mobile unit and reported to the directionalantenna(s). Thus, in this embodiment, it is the directional antenna(s)that transmit(s) data that is received and measured by the mobile unit.

In either case, as is known in the art, the received signal levelgenerally declines for larger radio distances from the signal source,e.g. the directional antenna or mobile unit. Thus, for the directionalantenna, the received signal level declines for larger radio distancesfrom the antenna towards the border of the cell edge, in particular forthe angular movement towards the cell border. This radio distancereflects the power loss moving away from the signal source. Note thattwo points with same radio distance from the source do not necessarilyhave to have the same geographical distance to that signal source.Mountains, buildings and similar objects may partially block or reducethe signals as received by the receiving unit, leading to a largerpropagation loss in some directions.

Furthermore, the received signal level associated with the directionalantenna unit and preferably also with the neighboring directionalantenna unit should preferably exceed a second threshold T₂. The portionof the antenna beam that does not fulfill these two conditions is thendefined as the main beam sector.

The values of the first T₁ and second T₂ thresholds are preferablydetermined by the handover parameter settings used in the system. Asingle or multiple handover parameters may be used in determining thevalues of T₁ and T₂. Furthermore, the same handover parameter(s) ordifferent parameters can be used in generating the two thresholds T₁ andT₂.

FIG. 7 is an antenna diagram illustrating the antenna beam or radiocoverage 40, 60 of two neighboring directional antenna units arranged ina RBS. The antenna beams 40, 60 of these antennas have been optimized bythe embodiment discussed in connection to FIG. 6 above. Thus, theantenna beam 40 of the directional antenna unit is (virtually) dividedinto at least a handover beam sector 42 and a main beam sector 44. Incases where the base station, in which the directional antenna isarranged, provides radio coverage in a general area, a correspondingantenna beam will be provided left of the beam 40 in the figure. In sucha case, the antenna beam 40 will include a first handover beam sector42, the main beam sector 44 and a second handover beam sector (notillustrated). However, it could be possible that the base station onlyprovides radio coverage within a portion of the area so that the antennabeam 40 and its directional antenna unit only has a single neighboringbeam 60 and directional antenna unit, respectively, of the same basestation, as is illustrated in the figure. In such a case, the main beamsector 44 could constitute the remaining portion of the beam sector 40in addition to the handover beam sector 42.

As is illustrated in the figure, within the handover beam sector 42, thedifference in received signal level associated with the two neighboringdirectional antenna units is smaller than the first threshold T₁.Furthermore, the received signal level associated with the directionalantenna unit and preferably also of the neighboring directional antennaunit is above the second threshold T₂ in this handover beam sector 42.

In order to maximize the performance of the radio communications system,the antenna beam sector shape or pattern and the handover parametersettings and, thus, the thresholds T₁ and T₂ should be optimized so thatthe antenna gain in the handover beam sector 42 exceeds the minimumthreshold T_(min) and preferably the angular interval of the handoverbeam sector 42 is larger than the angular threshold T_(A). The value ofthe threshold T₁ is as small as possible, while the received signallevels in the beam sector 42 are as high as possible over the thresholdT₂. Furthermore, the antenna gain in the main beam sector 44 ispreferably maximized.

As is evident from the antenna diagram of FIG. 7, in this exampleembodiment, the resulting optimization of different sub-sectors 42, 44of the antenna beam 40 of the directional antenna will generate anoverall beam shape that differs from the general smooth “cosine-shape”or “tear-shape” of prior art antennas. Instead, the radio coverage inthe handover beam sector 42 is typically larger than for prior artsolutions, which will result in the “knee-shaped” appearance of theantenna beam 40 in this beam sector 42. This increase in radio coveragein the handover area or beam sector 42 will result in a similar radioperformance and coverage of the prior art MRC-based (or equivalentcombining) softer handover procedures.

It is anticipated, that in some situations the gain of the directionalantenna within the handover beam sector 42 may actually be decreased,e.g. due to a change of the handover parameters or the thresholds(T_(min)). However, generally the directional antenna provides, more orless, always a higher gain level in the handover region or beam sector42 compared to prior art systems with MRC and equivalent techniques.

FIG. 8 is an illustration of another antenna diagram of two directionalantenna beams 40, 60 optimized. In this embodiment, the antenna beam 40,60 has an asymmetric shape with a maximum gain (radio coverage) in orclose to the handover beam sector 42. As one follows the antenna beam 40from the handover beam sector 42 and maximum gain, into the main beamsector 44 the received signal energy (maximum radio distance) willgradually decline. However, entering the handover beam sector 42 or theother end of the beam sector (which may be a second handover beam sectoror constitute a portion of the main beam sector), the maximum allowableradio distance will fall rapidly per traveled distance in order toreduce interference with adjacent cells and not spreading the signalenergy of the directional antenna far into neighboring cells.

Similar to FIG. 7, the received signal level in the handover beam sector42 exceeds a second threshold T₂ and the difference in received signallevel of the two neighboring directional antenna units in this handoverbeam sector 42 is smaller than a first threshold T₁. The values of therespective thresholds T₁ and T₂ are determined based on the settings ofthe handover parameters of the system, as was discussed above.

This principle of dividing the antenna beam in different beam sectorsand then performing a differential optimization of the beam sectorshapes in order to provide an increased antenna gain in the handoverarea can also be extended to a division of the antenna beam into morethan two beam sectors.

FIG. 9 is a flow diagram of an embodiment of the jointly processing stepof FIG. 3. The method continues from step S3 of FIG. 3. In the next stepS31, signal or link qualities of the communications links to the mobilestation are determined and compared for the at least two directionalantenna units. These link qualities can be calculated or estimated basedon measurement data obtained from the mobile unit and/or from theantenna units. Typical, non-limiting, examples of link qualities thatcan be used includes SNR (Signal to Noise Ratio), SIR (Signal toInterference Ratio), BLER (Block Error Ratio), BER (Bit Error Ratio) andBEP (Bit Error Probability). Based on the comparison of the linkqualities, a communications link is selected in step S32. Thiscommunication link is the link (of the compared links) having thecurrent highest or best link quality as determined based on thecomparison. The processed user data is generated based on the detecteduser data associated with the selected link in step S33. The method thenends.

Thus, by selecting the currently most suitable communications link, thedetected user data with a most correct data content is selected forfurther processing in the system. In cases where the detected dataincludes a control and payload data portion, the signal qualityestimation can be determined based on measurements on the controlportion, the payload portion or both of the control and payload portion.

The steps S31 to S33 of FIG. 9 are preferably performed on acommunications block or frame basis. This then enables the selection ofthe presently “best” detected user data at any time instance.Alternatively, the quality measure generation and comparison and thedata selection could be performed periodically or intermittently. Insuch a case, the detected user data stream associated with the selectedlink will then be used for the generation of the processed user datauntil a new comparison is performed.

Furthermore, the steps S31 to S33 can be performed in the RBS, in whichthe directional antenna units are arranged. Alternatively, the steps canbe performed in external unit, e.g. a RNC connected to the RBS. Thismeans that the intra-site handover will be handled as a conventionalsoft handover by the RNC, including the separate cell dataflow over theRNC-RBS interface. This results in a change of RNC configuration so thatsectors or cells within sites are configured as independent cells, i.e.all handover areas are configured as soft handover areas and no softerhandover areas will be present in the system.

FIG. 10 is a flow diagram illustrating another embodiment of the jointlyprocessing step of FIG. 3. The method continues from step S3 of FIG. 3.In a next step S41, the information content of the first and seconddetected user data from the two neighboring directional antenna unitsare then combined. The result of such a data combining is the processeduser data. By using information from both the detected user data asbasis for the processed user data generation, a higher radio performanceand coverage can typically be provided by the directional antennascompared to using a single user data source. This will then result inthat the system will be able to correctly interpret and process userdata originating from a mobile unit also in certain far-out regions,where the received user data typically would be so poor that asuccessful processing would be next to impossible if only one of the twodetected user data flows would be used in the processed user datageneration. As a consequence, larger radio coverage in the handover areais often obtained with this embodiment compared to the selectionembodiment.

As was discussed above, the step S41 can be performed in the RBS or inan external unit, e.g. RNC. Furthermore, the data combining of step S41can be performed solely on the payload data portion or the control dataportion. Alternatively, the whole detected user data (control andpayload) can be used in the combination process.

FIG. 11 is a flow diagram illustrating an embodiment of the user datasignal detecting step of FIG. 3. In this embodiment a directionalantenna unit includes at least two receivers (multiple antennas or agroup antenna) in order to provide uplink diversity reception. Themethod continues from step S1 of FIG. 3. In step S51, a firsttransceiver (receiver) of a directional antenna unit receives the userdata signal(s) originating from the mobile unit. Correspondingly, instep S52 a second transceiver of the same directional antenna unitreceives the user data signals. These user data carrying signals theninclude similar information content as the signals received by the firsttransceiver. In a next step S53, the first detected (and demodulated)user data is generated based on the received user data signals of thefirst and second transceiver. This step includes signal detection andselection or combining, e.g. MRC, as is known in the art. The methodthen continues to step S3 of FIG. 3. Note that the steps S51 to S53 canalso be performed for the second neighboring directional antenna unit inthe RBS.

FIG. 12 is a schematic block diagram of an embodiment of a (radio) basestation 100. The base station 100 includes directional antenna units140, 160 that provides radio coverage within different cells or sectorsof the total radio coverage area of the base station 100. In the figure,the base station 100 has been illustrated with only two directionalantenna units 140, 160. However, this should merely been seen as anillustrative non-limiting example and the base station 100 couldalternatively include more directional antenna units 140, 160, e.g. 3,4, 6, 9 or 12. The directional antenna units 140 include at least onetransceiver TX1/RX1, TX2/RX2, or at least one transmitter and onereceiver each. These transceivers TX1/RX1, TX2/RX2 performs thecommunication with mobile units positioned in the cell of and connectedto the respective directional antenna unit 140, 160. In order to provideuplink diversity reception, the directional antenna unit 140, 160preferably includes at least two transceivers TX1/RX1, TX2/RX2. Thetransceivers TX1/RX1, TX2/RX2 are in particular arranged for receivinguser data carrying signals originating from the mobile unit.

The directional antenna unit 140, 160 preferably also includes a datasignal detector 145, 165 for performing the initial data signalprocessing and detection of the received user data signals. Thisdetector 145, 165 can include functionality for signal processing, e.g.demodulation, A/D conversion, user data regeneration and/or decoding.The input to this data detector 145, 165 is the user data signals asreceived from the associated transceiver(s) TX1/RX1, TX2/RX2. This datasignal detection and processing will generally imply a loss inperformance of data, e.g. as manifested in reduced radio coverage of theassociated antenna unit 140, 160. The detected user data from the datadetectors 145, 165 of the directional antenna units involved in theintra-site handover procedure is then forwarded to a user data processor130, either implemented in the base station 100 or provided elsewhere,e.g. in a RNC or BSC.

The user data processor 130 then jointly processes the detected userdata from the at least two data detectors 145, 165. This jointly dataprocessing could be implemented as a data content combining and/or datacontent selection, with or without additional side (soft) informatione.g. quality indicators or quality estimators. In either case, processeduser data is generated by the processor 130. This data can then beforwarded to other units in the communications system using for examplean input and output (I/O) unit 110. For example, the processed user datacan be transmitted to the RNC for further processing and/or transmissionto another mobile unit.

The base station 100 preferably also includes an antenna beam adjuster150 that is configured for generating antenna beam adjusting commands.Such commands will then cause a change in the antenna beam of thedirectional antenna units 140, 160 by adapting (increasing) the antennagain in the handover area. The adjustment command can provide the beamsector shape by controlling an antenna adjusting unit (not illustrated)that is arranged and connected to the directional antenna units 140,160. Such adjusting unit could then mechanically adjust, e.g. moveand/or rotate, a mechanical structure in the antenna units 140, 160 inresponse to the adjustment command in order to obtain the desired beamshape. Such a mechanical structure can be the baffles around the antennaradiators, the ground plane behind the antenna radiators and/or astructure that couples the energy from the radiators, e.g. secondaryradiators. If the directional antenna unit 140, 160 is a group antennawith multiple antennas, the command can, alternatively or in addition,cause the desired beam shape by adjusting the relative amplitude and/orphase excitations of the antennas. As the person skilled in the artunderstands, any procedure that results in an adjustment of the beamshape of an antenna could be used in order to cause the directionalantenna unit 140, 160 to modify the antenna gain in the handover area.This adjuster 150 can alternatively be implemented in another networknode, e.g. in the RNC. As was discussed above, both an increase and adecrease of the antenna gain in the handover area can be performed,depending on e.g. handover parameter or threshold values or any otherfeedback from the system.

The units 110 to 165 of the base station 100 may be implemented assoftware, hardware or a combination thereof. The units 110 to 165 mayall be implemented in the base station 100 in a single network node inthe communications system. Alternatively, the user data processor 130and/or antenna beam adjuster 150 can be implemented in other networknodes in the communications system. For example, the user data processor130 and/or antenna beam adjuster 150 may be arranged in a RNC, BSC orMSC (Mobile Switching Center) connected to and controlling operation ofmultiple base stations 100. In such a case, the data processor 130and/or adjuster 150 can process detected user data from and control theantenna beam shape of multiple base stations 100, respectively.

FIG. 13 is a schematic block diagram of an embodiment of the antennabeam adjuster 150 of FIG. 12. This adjuster comprises a beam widthadjuster 152 that generates an adjusting command that causes the gainincrease in the handover area of a directional antenna unit by adjustingthe (3 dB) beam width of the antenna. This beam width adjusting can beobtained by redistributing the directivity of the directional antennaunit in the horizontal dimension, possibly at the cost of the maximumpeak gain for the antenna unit.

The unit 152 of the antenna beam adjuster 150 may be implemented assoftware, hardware or a combination thereof. The unit 152 may beimplemented in a base station or in a more central network node, e.g.RNC.

FIG. 14 is a schematic block diagram of another embodiment of an antennabeam adjuster 150. The antenna beam adjuster 150 includes a beam sectordefiner 154 that is configured for defining multiple beam sectors of theantenna beam of a directional antenna unit. In a first embodiment, thedefiner 154 is adapted for (virtually) dividing the antenna beam into atleast a handover beam sector and a main beam sector. This beam sectordefiner 154 is preferably configured for defining the handover beamsector as the portion of the antenna beam in which the difference insignal levels (as measured by the directional antenna or as measured bythe mobile unit and then transmitted to the directional antenna)associated with the directional antenna unit and a neighboringdirectional antenna unit exceeds a first threshold value. Alternatively,or in addition, the signal level is preferably above a second thresholdwithin this beam sector. The values of the first and second thresholdare determined based on handover parameter data or other input data fromother units in the system. Such input data could state than one and thesame beam sector definition should be used for all directional antennaunits in the system, or alternatively different definitions could beemployed for different antenna units, e.g. if they are arranged in areaswith different expected traffic conditions. Furthermore, the beam sectordefinition of a given antenna unit could be fixed or change over time,e.g. based on new input data. The definer 154 preferably bases the beamsector definitions on signal level threshold values, which in turn maybe determined based on handover parameter settings or values. Thisthreshold data may be retrieved from the data storage (not illustrated)arranged in the adjuster 150. Alternatively, the definer 154 preferablyreceives the information used in the beams sector definition processfrom an external unit in the system. In another embodiment, at leastthree different beam sectors are defined.

A handover beam sector optimizer 156 is arranged in the beam adjuster150 for receiving information of the current beam sector definition fromthe definer 154 and for optimizing and adjusting the shape of thehandover beam sector in order to increase (or sometimes decrease,depending on current parameter values) the antenna gain in this beamsector. This beam sector optimizer 154 is preferably configured forgenerating an adjustment command that causes a directional antenna unitto provide an antenna gain in the handover beam sector that exceeds aminimum threshold. Furthermore, the adjustment command preferably also,or in addition, provides an angular interval or size of the handoverbeam sector above an angular threshold. The values of these thresholdsare determined based on handover parameter data e.g. as retrieved fromthe data storage.

The antenna beam optimizer 150 can optionally include an optimizer 158for adjusting the beam shape of the main beam sector. This optimizer 158preferably generates an adjustment command that causes the directionalantenna unit to maximize the antenna gain in this main beam sector.

The units 154 to 158 of the antenna beam optimizer 150 may beimplemented as software, hardware or a combination thereof. The units154 to 158 may all be implemented in the antenna beam optimizer 150.Alternatively, a distributed implementation is also possible with someor all units 154 to 158 implemented in the base station and/or RNC.

FIG. 15 is a schematic block diagram of an embodiment of a user dataprocessor 130. This processor 130 receives signal or link quality datafrom units that perform such quality measurements and estimations. Suchmeasuring units can be implemented in the directional antenna unitsand/or in the mobile units. In either case, the qualities are forwardedto a link quality comparator 132 that compares the qualities of thecommunications links between the mobile unit and different directionalantenna units provided in the same base station. This quality generationand comparison can be performed on control data, payload data and/orcontrol and payload data. The quality measures are preferably determinedon a per frame or block basis so that the comparator 132 can operate pereach frame or radio block. Alternatively, the quality comparison couldbe performed periodically or intermittently.

A communications link selector 134 then selects the communications linkand associated directional antenna unit with a best link quality. If thecomparison is performed on frame/block basis the selection will providethe current best communications link. A processed user data generator136 then generated processed user data based on the detected user dataassociated with the selected communication link or directional antennaunit. Thus, by selecting the currently most appropriate link thecorresponding detected user data typically includes the most correctdata content.

The units 132 to 136 of the user data processor 130 may be implementedas software, hardware or a combination thereof. The units 132 to 136 mayall be implemented in the user data processor 130. Alternatively, adistributed implementation is also possible with some or all units 132to 136 implemented in the base station and/or RNC.

FIG. 16 is a schematic block diagram of another embodiment of a userdata processor 130. This processor 130 includes a data combiner 138 thatis configured for combining the information content of the at least twodetected user data. Thus, by combining the two user data sets thequality of the resulting processed user data can be enhanced compared toif only one of the detected user data sets is used as the sole datasource. The combiner 138 could be configured for only combining thepayload or control data portion of the detected user data.Alternatively, the whole content of the detected user data is used inthe combining process. The generator 136 then generates the processeduser data based on these (combined and demodulated) detected user data.

Although not illustrated in the figure, the user data processor 130 ofFIG. 16 can include a similar link quality comparator or processor aswas discussed above in connection with FIG. 15. Thus, also side or softinformation, such as quality indicators or quality estimators, can beused in the data combining process. For example, instead by simplycombining the detected user data streams in the combiner 138, qualityindicators of the communications link associated with the respectivedata stream can be used for enabling a weighted data stream combining.Thus, the combiner 138 uses information from a link quality comparatorarranged in the user data processor 130 for generating weights to use inthe data combining. These weights are then applied to the data streamsso that, typically, a detected data stream originating from a link witha good link quality will be weighted higher than a data stream from apoor communications link.

Thus, in this embodiment there may be a choice in also using theadditional soft information (quality indicators or estimations) in thejointly processing of the detected user data.

The units 136 and 138 of the user data processor 130 may be implementedas software, hardware or a combination thereof. The units 136 and 138may all be implemented in the user data processor 130. Alternatively, adistributed implementation is also possible with some or all units 136and 138 implemented in the base station and/or RNC. In addition, a linkquality processor or comparator can be implemented in the user dataprocessor 130 for introducing soft information in the data processing.

FIG. 17 is a schematic block diagram of a radio network controller 300.The RNC 300 generally includes an I/O unit 310 for conductingcommunication with external units. The I/O unit 310 is in particularconfigured for received processed user data and/or detected user datafrom connected base stations. In an embodiment, the I/O unit 310 alsotransmits antenna beam adjusting commands to base stations.

An optional user data processor 330 is implemented in the RNC 300 forgenerating processed user data based on detected user data received froma base station. This processor 330 could be configured for operatingaccording to the data selection and/or combing process discussed abovein connection with FIGS. 15 and 16, respectively. The resultingprocessed user data can then be forwarded through the I/O unit 310 toother units in the communications system.

An optional beam adjust command generator 350 can be arranged in the RNC300 for generating beam adjusting commands that causes the directionalantenna units to increase their antenna gain in the handover areas. Thiscommand generator 350 can be operated according to the embodimentsdiscussed above in connection with FIG. 13 and/or FIG. 14. The commandgenerator 350 can then preferably control operation of multipledirectional antenna units provided in different base stations.

The units 310 to 350 of the RNC 300 may be implemented as software,hardware or a combination thereof. The units 310 to 350 may all beimplemented in the RNC 300. Alternatively, a distributed implementationis also possible with some or all units 310 to 350 implemented in thebase station and/or other network nodes.

It will be understood by a person skilled in the art that variousmodifications and changes may be made without departure from the scopeof the appended claims.

1. A method of processing user data in a communications systemcomprising a base station having multiple directional transceiver unitsand a mobile unit connected to a first and a second directionaltransceiver unit of said base station and positioned in a handover areaassociated with said first and second directional transceiver unit, saidmethod comprising the steps of: said first directional transceiver unitdetecting a user data carrying signal originating from said mobile unitand generating first detected user data based on said user data carryingsignal; said second directional transceiver unit detecting said userdata signal originating from said mobile unit and generating seconddetected user data based on said user data carrying signal; jointlyprocessing said first detected user data and said second detected userdata to provide processed user data; and increasing the antenna gain ofsaid first directional transceiver unit in said handover area forincrementing the radio performance of said first directional transceiverunit in said handover area.
 2. The method according to claim 1, whereinsaid antenna gain increasing step comprises increasing said antenna gainin said handover area in order to compensate for any radio performancereduction in said handover area caused by said user data signaldetection.
 3. The method according to claim 1, further comprisingcomparing the link quality of a communications link between said mobileunit and said first directional transceiver unit and of a communicationslink between said mobile unit and said second directional transceiverunit and said jointly processing step comprises the steps of: selectinga communications link having a highest link quality of said comparedcommunications links; and generating said processed user data based onthe detected user data generated by a directional transceiver unitassociated with said selected communications link.
 4. The methodaccording to claim 1, wherein said jointly processing step comprisesgenerating said processed user data by combining said first detecteduser data and said second detected user data.
 5. The method according toclaim 1, wherein said antenna gain increasing step comprises increasingthe 3 dE beam width of the beam sector of said first directionaltransceiver unit.
 6. The method according to claim 1, wherein saidantenna gain increasing step comprises the steps of defining a handoverbeam sector of the antenna beam of said first directional transceiverunit; and optimizing a shape of said handover beam sector based on ahandover parameter setting associated with said base station.
 7. Themethod according to claim 6, wherein said defining step comprisesdividing said antenna beam into at least said handover beam sector and amain beam sector.
 8. The method according to claim 6, wherein saidoptimizing step comprises providing an angular interval of said handoverbeam sector over an angular threshold determined based on said handoverparameter setting.
 9. The method according to claim 6, wherein saidoptimizing step comprises providing an antenna gain in said handoverbeam sector that exceeds a minimum threshold determined based on saidhandover parameter setting.
 10. The method according to claim 6, whereinsaid defining step comprises defining said handover beam sector as aportion of said antenna beam in which a difference in a received signallevel associated with said first transceiver unit and a received signallevel associated with said second transceiver unit is smaller than athreshold value determined based on said handover parameter setting. 11.The method according to claim 1, wherein said jointly processing step isperformed in a radio network controlling unit connected to andcontrolling operation of said base station.
 12. The method according toclaim 1, wherein said detected user data comprises a control dataportion and a payload data portion, wherein said jointly processing stepcomprises the step of processing said payload data portion of saiddetected user data.
 13. The method according to claim 1, wherein saiddetected user data comprises a control data portion and a payload dataportion, wherein said jointly processing step comprises the step ofprocessing said control data portion of said detected user data.
 14. Auser data processing system in a communications system comprising a basestation having multiple directional transceiver units and a mobile unitconnected to a first and a second directional transceiver unit of saidbase station and positioned in a handover area associated with saidfirst and second directional transceiver unit, said first and seconddirectional transceiver unit comprises transceiving circuitry forreceiving a user data carrying signal originating from said mobile unitand detection circuitry configured to generate first and second detecteddata based on said user data carrying signal, said system comprising: aprocessor for jointly processing said first detected user data and saidsecond detected user data to provide processed user data; and beamadjustment circuitry configured to increase the antenna gain of saidfirst directional transceiver unit in said handover area forincrementing the radio performance of said first directional transceiverunit in said handover area.
 15. The system according to claim 14,wherein said beam adjustment circuitry is configured for increasing saidantenna gain in order to compensate for any performance reduction causedby operation of said detection circuitry.
 16. The system according toclaim 14, further comprising a comparator for comparing the link qualityof a communications link between said mobile unit and said firstdirectional transceiver unit and of a communications link between saidmobile unit and said second directional transceiver unit and saidprocessor comprises: means for selecting a communications link having ahighest link quality of said compared communications links; and meansfor generating said processed user data based on the detected user datafrom the detection circuitry of a directional transceiver unitassociated with said selected communications link.
 17. The systemaccording to claim 14, wherein said processor comprises: means forcombining said first detected user data and said second detected userdata; and means for generating said processed user data based on saidcombined user data.
 18. The system according to claim 14, wherein saidbeam adjustment circuitry is configured for increasing the 3 dB beamwidth of the beam sector of said first directional transceiver unit. 19.The system according to claim 14, wherein said beam adjustment circuitrycomprises: means for defining a handover beam sector of the antenna beamof said first directional transceiver unit; and means for optimizing ashape of said handover beam sector based on a handover parameter settingassociated with said base station.
 20. The system according to claim 19,wherein said defining means is configured for dividing said antenna beaminto at least said handover beam sector and a main beam sector.
 21. Thesystem according to claim 19, wherein said optimizing means isconfigured for providing an angular interval of said handover beamsector over an angular threshold determined based on said handoverparameter setting.
 22. The system according to claim 19, wherein saidoptimizing means is configured for providing an antenna gain in saidhandover beam sector that exceeds a minimum threshold determined basedon said handover parameter setting.
 23. The system according to claim19, wherein said defining means is configured for defining said handoverbeam sector as a portion of said antenna beam in which a difference in areceived signal level associated with said first transceiver unit and areceived signal level associated with said second transceiver unit issmaller than a threshold value determined based on said handoverparameter setting.
 24. The system according to claim 14, wherein saidprocessor is provided in a radio network controlling unit connected toand controlling operation of said base station.
 25. The system accordingto claim 14, wherein said detected user data comprises a control dataportion and a payload data portion, wherein said processor is configuredfor jointly processing said payload data portion of said detected userdata.
 26. The system according to claim 14, wherein said detected userdata comprises a control data portion and a payload data portion,wherein said processor is configured for jointly processing said controldata portion of said detected user data.
 27. A base station havingmultiple transceiver units in a communications system, said base stationcomprising: a first directional transceiver unit connected to a mobileunit and comprises: transceiving circuitry configured to receive a userdata carrying signal originating from said mobile unit; and detectioncircuitry configured to generate first detected data from said receiveduser data carrying signal; a second transceiver unit connected to saidmobile unit and comprises: transceiving circuitry configured to receivesaid user data carrying signal originating from said mobile unit; anddetection circuitry configured to generate second detected data fromsaid received user data carrying signal; a processor configured tojointly process said first detected user data and said second detecteduser data to provide processed user data; and beam adjustment circuitryto increase the antenna gain of said first directional transceiver unitin said handover area for incrementing the radio performance of saidfirst directional transceiver unit in said handover area.
 28. The basestation according to claim 27, wherein said beam adjustment circuitry isconfigured for increasing said antenna gain in order to compensate forany performance reduction caused by operation of said detectioncircuitry.
 29. The base station according to claim 27, furthercomprising a comparator for comparing the link quality of acommunications link between said mobile unit and said first directionaltransceiver unit and of a communications link between said mobile unitand said second directional transceiver unit and said processorcomprises: means for selecting a communications link having a highestlink quality of said compared communications links; and means forgenerating said processed user data based on the detected user data fromthe detection circuitry of a directional transceiver unit associatedwith said selected communications link.
 30. The base station accordingto claim 27, wherein said processor comprises: means for combining saidfirst detected user data and said second detected user data; and meansfor generating said processed user data based on said combined userdata.
 31. The base station according to claim 27, wherein said beamadjustment circuitry is configured for increasing the 3 dB beam width ofthe beam sector of said first directional transceiver unit.
 32. The basestation according to claim 27, wherein said beam adjustment circuitrycomprises: means for defining a handover beam sector of the antenna beamof said first directional transceiver unit; and means for optimizing ashape of said handover beam sector based on a handover parameter settingassociated with said base station.
 33. The base station according toclaim 32, wherein said defining means is configured for dividing saidantenna beam into at least said handover beam sector and a main beamsector.
 34. The base station according to claim 32, wherein saidoptimizing means is configured for providing an angular interval of saidhandover beam sector over an angular threshold determined based on saidhandover parameter setting.
 35. The base station according to claim 32,wherein said optimizing means is configured for providing an antennagain in said handover beam sector over a minimum threshold determinedbased on said handover parameter setting.
 36. The base station accordingto claim 32, wherein said defining means is configured for defining saidhandover beam sector as a portion of said antenna beam in which adifference in a received signal level associated with said firsttransceiver unit and a received signal level associated with said secondtransceiver unit is smaller than a threshold value determined based onsaid handover parameter setting.
 37. The base station according to claim27, wherein said detected user data comprises a control data portion anda payload data portion, wherein said processor is configured for jointlyprocessing said payload data portion of said detected user data.
 38. Thebase station according to claim 27, wherein said detected user datacomprises a control data portion and a payload data portion, whereinsaid processor is configured for jointly processing said control dataportion of said detected user data.